1. Technical Field
The present invention relates to a liquid discharge apparatus and a residual vibration detection method.
2. Related Art
An inkjet printer, serving as a liquid discharge apparatus, that discharges a liquid (ink) in the form of liquid droplets from a head using an inkjet format (an inkjet head) and forms an image on a medium such as paper has conventionally been widely utilized, owing to the ease with which relative low-cost and high-quality printed products are obtained. The head of the inkjet printer has a piezoelectric element for causing a diaphragm to vibrate, a pressure chamber in which a liquid is held in the interior and the internal pressure is increased and decreased by the vibration of the diaphragm, and a plurality of nozzles provided to a nozzle surface of the head so as to communicate with the pressure chamber; a drive signal drives the piezoelectric element, causing the pressure of the pressure chamber to increase and decrease and thereby causing the liquid to be discharged from the nozzles.
Due in to an increase in the viscosity of the ink, admixture of air bubbles, adhesion of dust or paper particles, or the like, the head of the inkjet printer may in some instances experience a discharge malfunction, during which ink droplets are not discharged normally from some nozzles of the plurality of nozzles. When such a discharge malfunction takes place, dot loss occurs in the image that is printed, and this causes the image quality to be degraded; therefore, it is desirable to inspect the state of discharge.
In one example of a method of inspecting the state of discharge of a liquid, Japanese laid-open patent publication No. 2004-276544 discloses a method for outputting a drive signal to a piezoelectric element, detecting a residual vibration that follows the pressure change inside the pressure chamber caused by the drive signal, as a change in the electromotive force of the piezoelectric element, and determining the state of discharge of the ink from the nozzles based on the vibration pattern of the residual vibration.